The pyrolysis of polyfurfuryl alcohol was studied up to 600°C. Micropores appear in the carbon as early as 300°C along with a significant amount of mesopores. As the pyrolysis temperature is increased, microporosity is retained, but the mesoporosity disappears. At 600°C the material is microporous with a monodisperse pore size distribution centered at 4–5Å. Infrared, X-ray photoelectron, and nuclear magnetic resonance spectroscopies, in combination with thermogravimetric analysis provide evidence that between 300 and 400°C, both polyaromatic domains decorated with hydrogen and oxygen (hetero) atoms and partially decomposed polymer chains coexist. The unreacted polymer and heteroatoms induce mesoporosity by buffering the micropores created by polyaromatic domains. Raising the pyrolysis above 400°C releases the buffering material, thereby collapsing the mesopores.